Tonight and March 23. No doubt, Vivaldi's "Four Seasons" is one of the best-loved pieces of classical music, and this weekend the Colorado Symphony is offering two unusual chances to hear it. On March 21, the CSO sends a baroque ensemble south to Lone Tree for a program that also includes Bach's Concerto for 2 Violins, Strings and Continuo played by two fan favorites: concertmaster Yumi Hwang-Williams and associate concertmaster Claude Sim. The same lineup is repeated two days later at Montview Presbyterian Church as part of the "Stained Glass Series." The details: 8 p.m. March 21, Lone Tree Arts Center, 10075 Commons Street (720-509-1000 or lonetreeartscenter.org, $36-$48) and 2:30 p.m. March 23, Montview Presbyterian Church, 1980 Dahlia St. ( 303-623-7876 or coloradosymphony.org, $20-$30).